The present invention relates to sensors, and in particular to sensors such as Hall effect devices that include active offset compensation.
Sensors that include calibration abilities are well known. For example see published German patent application DE 37 86 487 T2, U.S. Pat. Nos. 4,951,236, 4,982,351, and 5,051,937. These sensors are often characterized by their precision, wide application, and relatively low manufacturing cost. To provide the requisite precision, either the transducer device or the associated signal processing must include signal conditioning/compensation logic to calibrate the device and correct for external effects (e.g., temperature). For example, this may be achieved by calibrating and signal-conditioning the transducer device directly, which often requires considerable expense. Alternatively, the appropriately designed signal processing device within the sensor may be signal-conditioned, calibrated, and adapted to the particular application of the sensor.
Signal processing devices are designed as electronic circuits and consequently can be economically manufactured and relatively easily adapted to the particular application. Furthermore, special measures can compensate for the undesirable influences (e.g., temperature) on the signal processing device and suppress/reduce the interferences to the measurement signal (e.g., noise) by the undesirable influences, thus resulting in a higher accuracy sensor device.
However, with such sensors, the signal processing device processes the measurement signal after it has been created by the transducer, and thus may garble the measurement signal, especially with respect to the time structure of the signal. For example, in the case of periodic or quasi-periodic measurement signals and/or in the case of signal evaluation by a threshold comparison, this may lead to inaccuracies with respect to the switch-over point and the phase behavior of the sensor.
Therefore, there is a need for a sensor device that includes error correction circuitry such as offset correction to mitigate the effect of the undesirable influences on the sensor.